Highly concentrated stable solutions of color-forming agent: for pressure-sensitive recording materials

ABSTRACT

Highly concentrated stable solutions of color-forming agents of the general formula ##STR1## wherein x denotes hydroxyl, alkoxy, alkenyloxy, aralkoxy, cycloalkoxy, aryloxy, acyloxy, alkylamino, dialkylamino, acylamino, aralkylamino or arylamino and 
     R denotes alkyl, alkenyl or aralkyl, 
     further isocyclic or heterocyclic rings can be fused onto the rings A, B, C and D and the cyclic and acyclic radicals and the rings A, B, C and D can carry further non-ionic substituents which are customary in dyestuff chemistry, or mixtures thereof, in water-insoluble organic solvents from the group comprising optionally chlorinated hydrocarbons, vegetable oils and phthalic acid esters are used for the preparation of pressure-sensitive recording materials.

This is a division of application Ser. No. 010,932, filed 2-5-87 nowallowed as U.S. No. 4,783,196.

The invention relates to highly concentrated stable solutions ofcolour-forming agents of the general formula ##STR2## wherein x denoteshydroxyl, alkoxy, alkenyloxy, aralkoxy, cycloalkoxy, aryloxy, acyloxy,alkylamino, dialkylamino, acylamino, aralkylamino or arylamino and

R denotes alkyl, alkenyl or aralkyl,

further isocyclic or heterocyclic rings can be fused onto the rings A,B, C and D and the cyclic and acyclic radicals and the rings A, B, C andD can carry further non-ionic substituents which are customary indyestuff chemistry, or mixtures thereof, in water-insoluble organicsolvents from the group comprising optionally chlorinated hydrocarbons,vegetable oils and phthalic acid esters, their preparation and their usefor the preparation of pressure-sensitive recording materials andmicrocapsules with capsule walls which are produced by interfacialreaction processes.

Non-ionic substituents which are customary in dyestuff chemistry are,for example, halogen, hydroxyl, alkoxy, alkenyloxy, aryloxy, aralkoxy,cycloalkoxy, heteryloxy, aryl, heteryl, alkylmercapto, arylmercapto,aralkylmercapto, alkylsulphonyl, cyano, carbamoyl, alkoxycarbonyl,amino, which can be substituted by 1 or 2 alkyl, cycloalkyl, aryl oraralkyl groups, preferably to form a 5- or 6-membered ring, or thesubstituents of which can be cyclized, acylamino, alkenyloxy,alkylcarbonyloxy and arylcarbonyloxy, and, as substituents of the rings,also alkyl, aryl, aralkyl, nitro, alkenyl and arylvinyl.

Alkyl represents C₁ -C₃₀ -alkyl, in particular C₁ -C₁₂ -alkyl.

The alkyl radicals and the alkyl radicals in alkoxy, alkylthio,alkylamino, alkanoylamino, alkylsulphonyl and alkoxycarbonyl groups canbe branched and can be substituted, for example, by fluorine, chlorine,C₁ - to C₄ -alkoxy, cyano or C₁ -C₄ -alkoxycarbonyl.

Aralkyl is, in particular, phenyl-C₁ - to -C₄ -alkyl, which can besubstituted in the phenyl nucleus by halogen, C₁ - to C₄ -alkyl and/orC₁ - to C₄ -alkoxy.

Cycloalkyl is, in particular, cyclopentyl or cyclohexyl, optionallysubstituted by methyl.

Alkenyl is, in particular, C₂ -C₅ -alkenyl, which can be monosubstitutedby hydroxyl, C₁ - to C₄ -alkoxy, cyano, C₁ - to C₄ -alkoxycarbonyl,chlorine or bromine. Vinyl and allyl are preferred.

Halogen is, in particular, fluorine, chlorine or bromine, preferablychlorine.

Aryl is, in particular, phenyl or naphthyl which is optionallysubstituted by one to three substituents from the group comprising C₁ -to C₄ -alkyl, chlorine, bromine, cyano, C₁ - to C₄ -alkoxycarbonyl andC₁ - to C₄ -alkoxy.

Alkoxy is, in particular, C₁ -C₂ -alkoxy which is optionally subsitutedby chlorine or C₁ -C₄ -alkoxy.

Acyl is, in particular, C₁ - to C₄ -alkylcarbonyl or C₁ - to C₄-alkoxycarbonyl, or aminocarbonyl or aminosulphonyl which is optionallymono- or disubstituted by C₁ -C₄ -alkyl, phenyl or benzyl.

Alkoxycarbonyl is, in particular, C₁ - to C₄ -alkoxycarbonyl which isoptionally substituted by hydroxyl, halogen or cyano.

Heteryl is, in particular, pyridyl, pyrimidyl, pyrazinyl, triazinyl,indolyl, imidazolyl, oxazolyl, thiazolyl, triazolyl, thiadiazolyl ortetrazolyl, which can be benzo-fused, or their partly hydrogenated orcompletely hydrogenated derivatives.

The rings can be substituted by non-ionic substituents, in particular byC₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, cyano, nitro or halogen.

Of the colour-forming agents of the formula I, compounds which are ofparticular importance are those of the formula ##STR3## wherein X¹denotes hydroxyl, C₁ -C₁₂ -alkoxy which is optionally substituted bychlorine or C₁ -C₄ -alkoxy, C₂ -C₁₂ -alkenyloxy, benzyloxy which isoptionally substituted by C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy or halogen orphenethyloxy,

R¹ denotes C₁ -C₁₂ -alkyl or benzyl,

R², R⁴, R⁶ and R⁷ independently of one another denote hydrogen,chlorine, C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy, phenoxy, benzyloxy or aradical of the formula ##STR4## R³, R⁵ and R⁸ independently of oneanother denote hydrogen, chlorine, C₁ -C₁₂ -alkyl, C₂ -C₁₂ -alkenyl, C₁-C₁₂ -alkoxy or C₂ -C₁₂ -alkenyloxy, or phenyl, benzyl, phenoxy orbenzyloxy which is optionally substituted by chlorine, C₁ -C₁₂ -alkyl orC₁ -C₁₂ -alkoxy, or cyclohexyloxy or cyclopentyloxy which is optionallysubstituted by C₁ -C₁₂ -alkyl, or C₁ -C₁₂ -alkylmercapto or a radical ofthe formula ##STR5## Y¹ and Y² independently of one another denote C₁-C₁₂ -alkyl which is optionally substituted by chlorine, cyano, C₁ -C₄-alkoxycarbonyl or C₁ -C₄ -alkoxy, or cyclohexyl, phenyl or benzyl,which can be substituted by chlorine, C₁ -C₁₂ -alkyl or C₁ -C₁₂ -alkoxy,or

R² and R³ denote members which, together with ring A', and/or

R⁴ and R⁵ denote members, which, together with ring B', are necessary tocomplete a ring system of one of the following formulae ##STR6## Whereinin Y represents C₁ -C₁₂ -alkyl, which can be substituted by chlorine,cyano, C₁ -C₄ -alkoxycarbonyl or C₁ -C₄ -alkoxy, or cyclohexyl, phenylor benzyl, which can be substituted by chlorine, C₁ -C₁₂ -alkyl or C₁-C₁₂ -alkoxy, and

the saturated ring component can carry up to 4 radicals from the groupcomprising chlorine, C₁ - to C₄ -alkyl, C₁ - to C₄ -alkoxy and phenyl,or ##STR7## denotes a pyrrolo, pyrrolidino, piperidino, pipecolino,morpholino, pyrazolo or pyrazolino radical which is optionallysubstituted by chlorine, C₁ - to C₄ -alkyl or phenyl.

Examples of radicals which are substituted in the saturated ring are:##STR8##

Particularly preferred colour-forming agents are those of the formula##STR9## wherein X² denotes hydroxyl or C₁ -C₁₂ -alkoxy,

R^(3') denotes hydrogen, chlorine, C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy,benzyloxy, phenoxy or a radical of the formula ##STR10## R^(5') denotesC₁ -C₁₂ -alkoxy, benzyloxy or a radical of the formula ##STR11## R^(2'),R^(4'), R^(6') and R^(7') independently of one another denote hydrogen,chlorine, C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy, C₁ -C₄ -alkylamino or di-C₁-C₁₂ -alkylamino, or

R^(2') and R^(3') denote members which, together with the benzene ringto which they are bonded, are required to complete a ring system of oneof the formulae ##STR12## and R¹, X, Y¹ and Y² have the abovementionedmeaning.

Suitable (chloro)hydrocarbons for the solutions according to theinvention are high-boiling (150°-400° C.) (chloro)hydrocarbons which areliquid at room temperature, for example paraffins, in particular C₁₀-C₂₀ -n-paraffins, C₁₀ -C₂₀ -iso-paraffins and C₁₀ -C₁₇ -chloroparaffinswith a chlorine content of 15-70% by weight and their technical grademixtures, for example kerosine (C₁₀ -C₁₆ -paraffin) or white oils(50-70% paraffins and 30-50% naphthenes), aromatic hydrocarbons whichcontain alkyl groups with preferably 1-18 carbon atoms, such asalkyl-biphenyls, in particular iso-propylbiphenyl andtert.-butylbiphenyl, dialkyl-biphenyls, in particulardi-isopropylbiphenyl and di-tert.-butyl-biphenyl, alkyl- anddialkyl-naphthalenes, in particular iso-propylnaphthalene anddi-tert.-butyl-naphthalene, alkylbenzenes, in particular dodecylbenzene,hydrogenated and partly hydrogenated terphenyls, in particularcyclohexyldiphenyl, and diarylalkanes, in particular diphenyl ethane orethyldiphenylmethane.

Suitable vegetable oils are, for example, linseed oil, sesame oil, oliveoil, palm oil, groundnut oil, thistle oil, sunflower oil, castor oil,maize germ oil, soya bean oil and rape oil.

Suitable esters of phthalic acid are, for example those of C₂ -C₁₈-aliphatic alcohols, in particular dibutyl phthalate.

Preferred highly concentrated solutions contain 10-50% by weight, inparticular 10-35% by weight, of colour-forming agent.

The invention also relates to compounds of the formula (III) wherein R¹,X² and R^(2') -R^(7') have the abovementioned meaning but R^(3') andR^(5') do not simultaneously represent OCH₃ or OC₂ H₅ if R^(2') andR^(4') denote hydrogen, and furthermore R^(3') and R^(5') do notsimultaneously represent OCH₃ if R^(2') denotes hydrogen and R^(4')denotes 2-OCH₃.

The invention furthermore relates to a process for the preparation ofthe highly concentrated colour-forming agent solutions according to theinvention by reaction of dyestuff salts of the formula ##STR13## withbases of the formula

    MeX                                                        (V)

wherein

R, X and the rings A, B, C and D have the abovementioned meanings,

Me denotes an alkali metal or alkaline earth metal, in particular sodiumor potassium, and

An.sup.(-) denotes an anion from the series comprising Cl, Br, acetate,sulphate, phosphate and ##STR14## in an organic reaction mediumcustomary for these reactions, and either (a) a water-insoluble solventcontained in the solutions according to the invention is added, theresulting layers are separated after the reaction--if appropriate afteraddition of water--and the solution, according to the invention, of thecolour-forming agent in the water-insoluble solvent is then obtaineddirectly, or

(b) the reaction is carried out in the absence of a water-insolublesolvent contained in the solutions according to the invention, thecolour-forming agent is separated off from the reaction medium after thereaction and the water-insoluble solvent is then added.

Suitable reaction media are polar solvents, such as dimethylformamide,dimethylsulphoxide, hexamethylphosphoric acid triamide and alkanols.Dimethylformamide and C₁ -C₁₈ -alkanols are preferred.

Suitable reaction temperatures are between 20° and 120° C., and arepreferably 30°-80° C.

A particularly advantageous preparation process comprises a procedure inwhich, in a one-pot reaction, ketones of the formula ##STR15## arecondensed with amines of the formula ##STR16## or ketones of the formula##STR17## are condensed with a compound of the formula ##STR18## in thepresence of a condensing agent which donates an anion An.sup.(-), togive the colour salts of the formula (IV), and these are reacted withthe bases (V) as described above, without intermediate isolation.

Phosphorus oxychloride and/or diphosphorus pentoxide are therebypreferably employed as condensing agents.

The resulting colour-forming agent solutions can be marketed withoutfurther purification and used in pressure-sensitive recording materials,in particular in microencapsulated materials.

The colour-forming agent solutions are preferably enclosed inmicrocapsules, the walls of which are produced by interfacial creationprocesses.

Interfacial reactions, for example the condensation of organic acidchlorides and amines, are known. A summary of the interfacial reactionsso far disclosed can be found in G. Baxter, Microencapsulation Processesand Applications, published by J. E. Vandegaer.

Those microcapsules whose shells consist of polyaddition products ofpolyisocyanates and polyamines are used with particular preference.

Processes for producing microcapsules by the interfacial polyaddition ofpolyisocyanates and polyamines are for example described in GermanPublished Specifications 1,109,335; 2,251,381; 2,242,910; 2,120,921;2,311,712 and 2,523,586.

It has been found that the colour-forming agents of the formula (I) aresurprisingly readily soluble in the water-insoluble organic solventsmentioned. Solutions with a colour-forming agent content of up to 50% byweight, in particular 15-50% by weight, can be obtained.

They have an excellent stability, even under variations in temperature.

For use in the recording materials, they are diluted with the solventsof the solutions according to the invention to concentrations of about3-10% by weight.

On contact with an acid developer, that is to say an electron acceptor,the solutions according to the invention give intense blue, green-blue,green, violet or red colour shades which are excellently fast tosublimation and light. Navy blue, grey or black dyeings can be achievedby mixtures with one another.

They are also useful when mixed with one or more other knowncolour-forming agents, for example 3,3-bis-(aminophenyl)-phthalides,3,3-bis-(indolyl)-phthalides, 3-amino-fluoranes, 2,6-diamino-fluoranes,leuco-auramines, spiropyrans, spirodipyrans, chromenoindoles,phenoxazines, phenothiazines, carbazolyl-methanes or othertriarylmethane leuco-dyestuffs, to give green, violet, blue, navy blue,grey or black dyeings.

Both on phenolic substrates and on activated clays they have a goodcolour intensity, high fastness to light and an excellent stabilitytowards ageing and CB. They are suitable for a pressure-sensitiverecording material, which can be either a copying or a recordingmaterial. Their speed of development differs according to thesubstituents. In general, however, they are distinguished by a highspeed of development, with a simultaneously reduced sensitivity of therecording materials towards unintentional premature development.

Pressure-sensitive recording materials are known, for example, from U.S.Patent Specifications Nos. 2,800,457 and 2,800,458.

The solutions according to the invention offer diverse advantages:

In comparison with the pulverulent colour-forming agent formulations,they allow clean and easy handling. In addition to the colour-formingagent, they consist of a solvent suitable for microencapsulation and cantherefore easily be diluted or blended to the desired use concentrationby means of metering devices. They enable very deep prints to beproduced, since by using highly concentrated solutions, microcapsuleswith a colour-forming agent content above the previously customarycontent of 3-7% by weight can be prepared.

EXAMPLE 1

12.1 g (0.05 mol) of 4,4'-dimethoxybenzophenone and 9.2 g (0.05 mol) ofN-methyl-diphenylamine are suspended in 38.2 g (0.25 mol) of phosphorusoxychloride, and 14.2 g (0.1 mol) of phosphorus pentoxide are added atroom temperature. The melt is stirred at this temperature for 18 hoursand discharged onto 500 ml of ice-water and the mixture is stirred atroom temperature for about a further 10-12 hours, until the dyestuffseparates out as crystals. Filtration with suction, washing with waterand drying in vacuo at 40° C. gives 21.8 g (98% of theory) of a reddishpowder of melting point 78°-81° C.

13.4 g (0.1 mol) of 30% strength sodium hydroxide solution are slowlyadded dropwise to a solution of 17.8 g (0.04 mol) of this dyestuff in140 ml of dimethylformamide at 40° C. The mixture is stirred at 40° C.for 2 hours and filtered and the filtrate is discharged onto 500 ml ofice-water. On addition of 25 g of sodium chloride, an almost colourlessprecipitate separates out and is filtered off. It is rinsed with 100 mlof 2% strength sodium hydroxide solution and cold water. Drying in vacuoat 40° C. gives 14.2 g (83.4% of theory) of an almost colourlesscrystalline powder of melting point 48°-54° C. and of the formula##STR19##

A solution in glacial acetic acid becomes red-violet with λ_(max) =556nm and λ₂ =430 nm. ¹ H-NMR spectrum (CDCl₃): δ=1.64 ppm (S, 1H), δ=3.26ppm (S, 3H), δ=3.73 ppm (S, 6H).

11.4 g of the moist press-cake of the carbinol base of the formula (1)are dissolved in 32 g of chloroparaffin (C₁₃ -C₁₈ -n-paraffin with about45% by weight of chlorine) or diisopropylnaphthalene. After removal ofthe residual water in vacuo at 40°-50° C., solutions which contain about20% of colour-forming agent are obtained. The solutions can easily bediluted to the customary use concentrations in recording materials of,for example, 3% or 5% with white oil (62% n-paraffin/38% naphthene) orkerosine (C₁₀ -C₁₆ -n-paraffin), and can be encapsulated by customarymethods. A strong red-violet colour is developed on acid clay.

EXAMPLE 2

If 9.6 g of sodium butylate are used instead of 13.4 g of 30% strengthsodium hydroxide solution in the preparation of the carbinol basederivaive in Example 1, the reaction gives a pale yellow oil which canbe dissolved to the extent of 35% in chloroparaffin (C₁₃ -C₁₈-n-paraffin with about 45% of chlorine), 30% in diisopropyldiphenyl and30% in linseed oil. The compound corresponds to the formula ##STR20##

EXAMPLE 3

44.3 g (0.1 mol) of the dyestuff described in Example 1(4,4'-dimethoxy-4"-N-methyl-N-phenyl-triphenylmethyl chloride) and 93 gof diisopropylnaphthalene are dissolved in 500 ml of methanol. 40 g (0.3mol) of 30% strength sodium hydroxide solution are added dropwise at 40°C. and the mixture is stirred at this temperature for 6 hours.Thereafter, 120 ml of water are added, the mixture is stirred for 30minutes and the organic phase which separates out as the lower phase isseparated out. After removal of the residual water in vacuo at 40° C.and filtration with suction, 126 g of a yellowish solution containing29.7% of colour-forming agent which can be developed are obtained.(According to the E₁ ¹ measurement in glacial acetic acid). The ¹ H--NMRspectrum shows that the colour-forming agent consists of a mixture ofabout 90% of 4,4'-dimethoxy-4"-N-methyl-N-phenyltriphenyl-carbinolmethyl ether (formula 1: OCH₃ instead of OH) and about 10% of carbinolbase of the formula 1.

The solution can readily be diluted to use concentrations in recordingmaterials of 3%, 5% or 7% with further diisopropylnaphthalene,chloroparaffin (C₁₂ -C₁₈ -n-paraffin, about 45% of chlorine), sesame oilor linseed oil, and incorporated into polyamide, gelatine, polyurethaneor polyurea microcapsules. Strong red-violet colour shades are obtainedon acid clay or bisphenol A.

EXAMPLE 4

A suspension of 13.6 g (0.05 mol) of 2,4,4'-trimethoxy-benzophenone and9.2 g (0.05 mol) of N-methyldiphenylamine in 38.2 g (0.25 mol) ofphosphorus oxychloride are taken and 14.2 g (0.1 mol) of phosphoruspentoxide are added in portions at room temperature. The reactionmixture is warmed to 40° C. and stirred at this temperature for 15hours. Thereafter, it is discharged onto 600 ml of ice-water andsubsequently stirred at room temperature for about 10 hours and thecolour resin which has separated out is decanted off. The residue istreated with 600 ml of 10% strength hydrochloric acid and 300 ml ofwater in succession. Drying in vacuo at 40° C. and grinding gives 22 gof a dark red powder with a melting range of 56°-62° C.

A solution of 14.2 g (0.03 mol) of this dyestuff in 80 ml ofdimethylformamide is filtered, and 18 g (0.09 mol) of 20% strengthsodium hydroxide solution are slowly added at room temperature. Themixture is stirred at 40° C. for 1 hour and filtered and the filtrate ispoured into 600 ml of ice-water. 50 g of sodium chloride are added andthe mixture is stirred briefly. The pale yellow crystalline precipitateis filtered off with suction and washed with 100 ml of 2% strengthsodium hydroxide solution and 200 ml of water. Drying gives 11.9 g(86.8% of theory) of a pale yellow powder of melting point 107°-112° C.(from methylcyclohexane), and of the formula ##STR21##

A solution in glacial acetic acid becomes dark violet with λ_(max) =563nm and λ₂ =456 nm. ¹ H--NMR spectrum (CDCl₃): δ=3.27 ppm (S, 3H), δ=3.64ppm (S, 3H), δ=3.73 ppm (S, 3H), δ=3.77 ppm (S, 3H) and δ=5.04 ppm (S,1H). 10 g of the dried press-cake of the formula (3) can be dissolvedcompletely in 40 g of chloroparaffin (C₁₃ -C₁₈ -n-paraffin containingabout 45% by weight of chlorine). Stable chloroparaffin solutions whichcontain 20% of colour-forming agent and can easily be diluted to thecustomary use concentrations in recording materials (3% or 5%) areobtained in this manner. A strong dark-red to violet colour with high CFand CB fastnesses is achieved on acid clay.

EXAMPLE 5

20-30% strength solutions of the following colour-forming agents inchloroparaffin (C₁₃ -C₁₈ -n-paraffin containing about 45% of chlorine),diisopropylnaphthalene, diisopropyl-biphenyl, sesame oil or linseed oilare prepared analogously to Example 1, 2 and 3:

                                      TABLE 1                                     __________________________________________________________________________     ##STR22##                                                                    Formula                            Colour shade on acid                                                                     λ.sub.max in             No.  a       b    Q        X       clay or bisphenol A                                                                      glacial acetic                  __________________________________________________________________________                                                  acid                            4    3-OCH.sub.3                                                                           4-OCH.sub.3                                                                        CH.sub.3 OCH.sub.3                                                                             lilac      568 nm                               4-OCH.sub.4                                                              5    3-OCH.sub.3                                                                           3-OCH.sub.3                                                                        CH.sub.3 OC.sub.3 H.sub.7 -i                                                                   violet     565 nm                               4-OCH.sub.3                                                              6    4-OCH.sub.4                                                                           4-CH.sub.3                                                                         C.sub.4 H.sub.9                                                                        OH/OCH.sub.3                                                                          red        530 nm                               2-OCH.sub.3                                                              7    4-OCH.sub.3                                                                           4-C.sub.3 H.sub.7 -i                                                               C.sub.3 H.sub.7 -n                                                                     OC.sub.3 H.sub.7 -i                                                                   red        528 nm                               3-OCH.sub.3                                                              8    4-OCH.sub.3 3-OCH.sub.3                                                               2-Cl                                                                                ##STR23##                                                                             OH/OCH.sub.3                                                                          orange-red 510 nm                          9    4-OCH.sub.3                                                                           2-OCH.sub.3                                                                        CH.sub.3 OH/OC.sub.6 H.sub.13                                                                  claret     --                                   5-Cl                                                                     10   4-OCH.sub.3                                                                           2-C.sub.3 H.sub.7 -i                                                               CH.sub.3 OH/OC.sub.3 H.sub.7 -i                                                                red        485 nm                                       4-C.sub.3 H.sub.7 -i                                             11   4-OCH(CH.sub.3).sub.2                                                                 2-CH.sub.3                                                                         C.sub.2 H.sub.5                                                                        OC.sub.6 H.sub.13                                                                     orange-red --                                   2-OCH(CH.sub.3).sub.2                                                    12   4-SCH.sub.3                                                                           4-OCH.sub.3                                                                        C.sub.2 H.sub.5                                                                        OCH.sub.2C.sub.6 H.sub.5                                                              dark red-blue                                                                            --                                   2-CH.sub.3                                                               13   2-OCH.sub.3                                                                           4-OCH.sub.3                                                                        CH.sub.3 OC.sub.4 H.sub.9                                                                      lilac-red  556 nm                               3-OCH.sub.3                                                                   4-OCH.sub.3                                                              14   4-OC.sub.2 C.sub.4 OCH.sub.3                                                          4-OCH.sub.3                                                                        CH.sub.3 OC.sub.2 H.sub.4 OCH.sub.3                                                            red-violet 554 nm                          15   4-OC.sub.4 H.sub.9                                                                    4-OCH.sub.3                                                                        CH.sub.3 OH      dark red-violet                                                                          558 nm                                       3-C.sub.3 H.sub.7 -i                                                          5-C.sub.3 H.sub.7 -i                                             16   4-C.sub.12 H.sub.25                                                                   4-OCH.sub.3                                                                        CH.sub.3 OH      raspberry red                                                                            528 nm                                       2-OCH.sub.3                                                      17   4-OC.sub.2 H.sub.5                                                                    2-OCH.sub.3                                                                        C.sub.2 H.sub.5                                                                        OC.sub.2 H.sub.5                                                                      wine red   544 nm                                       4-CH.sub.3                                                                    5-Cl                                                             __________________________________________________________________________

EXAMPLE 6

A solution of 24.5 g (0.05 mol) of the dyestuff of the formula ##STR24##in 200 ml of methanol is added dropwise to a solution of 10.8 g (0.2mol) of sodium methylate and 50 g of chloroparaffin (C₁₃ -C₁₈-n-paraffin containing about 45% of chlorine) in 500 ml of methanol at40° C. in the course of 30 minutes. The mixture is stirred at 40° C. for2 hours and 250 ml of water are then added. The lower organic phase isseparated off and washed with water and the residual water is removed invacuo at 40° C. Filtration with suction gives 68 g of a pale yellow oilwhich, according to the E₁ ¹ measurement, contains 28% (78.7% of theory)of the carbinol base derivative of the formula ##STR25## A strong greencolour shade with λ_(max) =627 nm and λ2=436 nm is developed in glacialacetic acid.

The solution can easily be diluted to the desired use concentration withkerosine (C₁₀ -C₁₆ -n-paraffins), dodecylbenzene, diisopropylnaphthaleneor further chloroparaffin (C₁₃ -C₁₈ -n-paraffin containing about 48% ofchlorine). When encapsulated in gelatine, polyamide, polyurethane orpolyurea materials, the compound gives a colourless green with goodfastness to light and ageing on acid clay or salicylate.

A mixture of the colour-forming agents of the formula (1) and (18) in arati of about 2:1 gives a deep neutral black with high ageing and CBstability on acid clay.

EXAMPLE 7

43.4 g (0.13 mol) of 4-(N-methyl-N-phenyl)amino-4'-methoxy-benzophenone,95% pure, and 24.7 g (0.2 mol) of phosphorus pentoxide are added insuccession to a solution of 23.8 g (0.13 mol) of N-methyldiphenylamineand 96.6 g (0.63 mol) of phosphorus oxychloride at room temperature. Theimmediately greenish-coloured reaction mixture is stirred at 50° C. for20 hours. The melt is cooled to 20° C. and then dissolved in 500 ml ofmethanol, with thorough stirring. The temperature is kept below 50° C.by external cooling. 100 ml of toluene and 109 g ofdiiso-propylnaphthalene are added in succession to the methanolicdyestuff solution. 370 g (2.78 mol) of 30% strength sodium hydroxidesolution are then added dropwise such that a temperature of about 40° C.is established. The mixture is then stirred at 40° C. for 3 hours.Thereafter, 200 ml of water are added and the aqueous phase whichseparates out as the lower phase is separated off. The toluene andresidual water are removed azeotropically from the organic phase under awaterpump vacuum. The yellowish-brown colour-forming agent solution isfiltered off and is ready for use in this form. Yield: 174.3 g, content:36% of colour-forming agent (93.8% of theory, according to E¹ ₁measurement in glacial acetic acid). The ¹ H--NMR spectrum shows thatthe colour-forming agent consists of a mixture of about 95% of carbinolbase methyl ether of the formula ##STR26## and about 5% of carbinol baseof the formula (20, OH instead of OCH₃). A solution in glacial aceticacid becomes green with λ_(max) =612 nm and λ₂ =478 nm. The solution canbe diluted without problems to the customary use concentrations inrecording materials with further diiso-propylnaphthalene, kerosine (C₁-C₁₆ -n-paraffin) or white oil (62% n-paraffin/38% naphthene), andincorporated into microcapsules. Strong green colour shades are obtainedon acid clay or bisphenol A. A mixture of the colour-forming agents ofthe formula (1) and (20) in a ratio of about 4:3 likewise gives a deepneutral black on acid clay.

EXAMPLE 8

20-30% strength solutions of the following colour-forming agents inchloroparaffin (C₁₃ -C₁₈ -n-paraffins containing about 45% by weight ofchlorine), diisopropylnaphthalene or linseed oil are also obtained inthe same manner as described in the above Examples 6 and 7:

    TABLE 2      ##STR27##             λ.sub.max'  in Formula No. a b Q X Colour shade on acid     clay glacial acetic acid       21 4-N(CH.sub.3).sub.2 4-OCH.sub.3 CH.sub.3 OCH.sub.3 blue-green 602     nm  2-OCH.sub.3 22 4-N(C.sub.2 H.sub.5).sub.2 4-Cl C.sub.3 H.sub.7 -i     OC.sub.3 H.sub.7 -i green 616 nm 23 4-NC.sub.2 H.sub.5 2-OCH.sub.3     C.sub.2 H.sub.5 OC.sub.2 H.sub.5 green 612 nm      ##STR28##             24     ##STR29##      4-OCH.sub.3 CH.sub.3 (OC.sub.2 H.sub.4).sub.2O CH.sub.3 green 610 nm     25      ##STR30##      4-OCH.sub.3 CH.sub.3 OH/OCH.sub.3 dark green 610 nm      26 4-N(CH.sub.2C.sub.6 H.sub.5).sub.2 -- CH.sub.3 OC.sub.6 H.sub.13     green 623 nm 27 4-N(CH.sub.3).sub.2 4-OC.sub.4 H.sub.9 -t CH.sub.3     OH/OCH.sub.3 turquoise 608 nm  2-Cl      28 4-N(CH.sub.3).sub.23-CH.sub.35-CH.sub.3      ##STR31##      CH.sub.3 OC.sub.4 H.sub.9 turquoise 606 nm  29 4-N(C.sub.2      H.sub.5).sub.2 4-N(C.sub.2 H.sub.5).sub.2 C.sub.2 H.sub.5 OC.sub.2     H.sub.5 blue 602 nm      30 4-OCH.sub.3     ##STR32##      CH.sub.2C.sub.6 H.sub.5 OC.sub.3 H.sub.7 -n green --      31 4-OCH.sub.32-OCH.sub.3      ##STR33##      C.sub.2 H.sub.5 OH/OCH.sub.3 blue-green --      32     ##STR34##      4-SC.sub.6 H.sub.5 CH.sub.2CHCH.sub.2 OC.sub.2 H.sub.5 dull green --     33 4-N(CH.sub.3).sub.2 4-N(CH.sub.2 C.sub.4 H.sub.9 OH/OC.sub.2 H.sub.5     blue 605 nm   C.sub.6 H.sub.5).sub.2  3-CH.sub.3  5-CH.sub.3 2-OC.sub.2     H.sub.5  34 4-C.sub.12      H.sub.25 2-CH.sub.3     ##STR35##      C.sub.12 H.sub.25 OCH.sub.3 dull green 620 nm      35 4-OCH.sub.3     ##STR36##       OCH.sub.3 dark green 614 nm      36 4-Cl2-Cl     ##STR37##      CH.sub.3 OC.sub.4 H.sub.9 grass green 620 nm  37 4-OC.sub.2 H.sub.5      ##STR38##      CH.sub.3 OH/OCH.sub.3 dark green 618 nm  38 4-C.sub.5      H.sub.11     ##STR39##      CH.sub.3 OH/OCH.sub.3 very dark green 625 nm      39     ##STR40##      ##STR41##      CH.sub.3 OH/OCH.sub.3 blue 609 nm      40     ##STR42##      ##STR43##      CH.sub.3 OC.sub.2 H.sub.5 blue 603 nm      41     ##STR44##      ##STR45##      ##STR46##      OCH.sub.3 blue 605 nm      42     ##STR47##      ##STR48##      C.sub.12 H.sub.25 OC.sub.3 H.sub.7 -i blue --      43     ##STR49##      ##STR50##      CH.sub.3 OH/OCH.sub.3 blue --  44 4-OC.sub.2      H.sub.5     ##STR51##      CH.sub.3 OC.sub.2 H.sub.5 dark green 614 nm  45 4-OCH.sub.32-OCH.sub.3      ##STR52##      CH.sub.3 OCH.sub.3 green --

EXAMPLE 9

31.5 g (0.13 mol) of 4,4'-dimethoxy-benzophenone and 28.4 g (0.2 mol) ofphosphorus pentoxide are added to a solution of 29.6 g (0.13 mol) of4-ethoxy-N-methyldiphenylamine in 96.6 g (0.63 mol) of phosphorusoxychloride at room temperature. The immediately pale violet-colouredreaction mixture is warmed to 40° C. and stirred at this temperature for6 hours. Thereafter, the melt is cooled to 20° C. and dissolved in 450ml of methanol. The temperature is kept below 50° C. by externalcooling. 500 g of 30% strength sodium methylate solution are addeddropwise to the dyestuff solution taken, with vigorous stirring, suchthat a temperature of between 30°-35° C. is established. The dropwiseaddition time is about 2 hours. During this period, a pale beige, almostcolourless precipitate separates out. The suspension is stirred at30°-35° C. for 10-15 hours. It is cooled to 10°- 15° C., 100 g of waterare added, the mixture is filtered with suction and the residue iswashed with methanol/water 1:1 and water in succession. 90.3 g of moistyield of the colour-forming agent ##STR53## containing 35% of water(corresponding to 93.3% of theory) are obtained. When dissolved in 235 gof chloroparaffin (C₁₃ -C₁₈ -paraffin containing about 45% by weight ofchlorine) and after removal of the residual water, a 20% strengthsolution which gives a deep dark red-violet dyeing with good fastnessproperties on acid clay is obtained.

After drying in vacuo at 40° C., a pale beige crystalline powder ofmelting point 116°-118° C. which develops a red-violet colour with aλ_(max) of 557 nm and λ₂ =428 nm in glacial acetic acid is obtained fromthe moist yield.

EXAMPLE 10

10-30% strength solutions of the following colour-forming agents areprepared in chloroparaffin (C₁₃ -C₁₈ -n-paraffin containing about 45% byweight of chlorine), diisopropylnaphthalene, diisopropylbiphenyl,linseed oil or sesame oil in the same manner as described in Example 9:

    TABLE 3      ##STR54##              Colour shade on λ.sub.max in Formula No. a b c d Q X     salicylate or phenolic resin glacial acetic acid       47 4-OC.sub.2 H.sub.5 4-OC.sub.2 H.sub.5 -- 4-OC.sub.2 H.sub.5     CH.sub.3 OH violet 558 nm 48 4-OCH.sub.3 4-OCH.sub.3 -- 4-OC.sub.2     H.sub.5 CH.sub.3 OC.sub.3 H.sub.7 -n violet 552 nm 49 4-OCH.sub.3     4-SCH.sub.3 -- 4-OC.sub.2 H.sub.5 CH.sub.3 OCH.sub.3 dark violet 568 nm      3-CH.sub.3 50 4-OC.sub.4 H.sub.9 4-N(CH.sub.3).sub.2 -- 4-OC.sub.2     H.sub.5 CH.sub.3 OH/OCH.sub.3 turquoise 618 nm   2-OCH.sub.3 51 4-OC.sub.     2 H.sub.5 4-SC.sub. 2 H.sub.5 -- 4-OC.sub.2      H.sub.5 CH.sub.3 OH blue-violet 570 nm 52 4-C.sub.3 H.sub.7      -i 4-N(C.sub.2 H.sub.5).sub.2 -- 4-OC.sub.2 H.sub.5 C.sub.3 H.sub.7 -i     OH green 626 nm  2-CH.sub.3 53 4-OCH.sub.3 4-OCH.sub.3 -- 4-OCH.sub.3     CH.sub.3 OH/OCH.sub.3 dark violet 564 nm   3-OCH.sub.3  2-OCH.sub.3 54     4-OCH.sub.3 4-OCH.sub.3 -- 4-OCH.sub.3 C.sub.4 H.sub.9 OC.sub.4 H.sub.9     dark violet 568 nm   2-OCH.sub.3  3-OCH.sub.3 55 4-OCH.sub.3 4-OCH.sub.3     2-OC.sub.2 H.sub.5 4-OC.sub.2 H.sub.5 C.sub.2 H.sub.5 OC.sub.3 H.sub.7     -i lilac 566 nm   3-OCH.sub.3 56 4-OCH.sub.3 4-N(C.sub.5 H.sub.11).sub.2     2-OC.sub.2 H.sub.5 4-OC.sub.2 H.sub.5 C.sub.2 H.sub.5 OC.sub.2 H.sub.5     green 615 nm  2-Cl  57 4-OCH.sub.2C.sub.6 H.sub.5 4-OCH.sub.2C.sub.6     H.sub.5 2-OCH.sub.3 4-CH.sub.3 CH.sub.3      ##STR55##      violet 552 nm  58 4-OC.sub.2 H.sub.4      OCH.sub.3     ##STR56##      2-C.sub.2 H.sub.5 4-Cl C.sub.2 H.sub.5 OH green 613 nm      59     ##STR57##      ##STR58##      -- 4-OC.sub.2 H.sub.5 C.sub.2 H.sub.5 OC.sub.2 H.sub.5 blue --  60      ##STR59##      ##STR60##      -- 4-CH.sub.3 C.sub.4 H.sub.9 -n OH/OCH.sub.3 blue  61 4-OC.sub.2     H.sub.5 4-C.sub.3 H.sub.7 -i -- 4-C.sub.6 H.sub.5 CH.sub.3 OC.sub.3     C.sub.7 -i red-violet  3-C.sub.3 H.sub.7 -i 2-C.sub.3 H.sub.7 -i  62      ##STR61##      ##STR62##      2-OCH.sub.3 4-OCH.sub.32-CH.sub.3 C.sub.4 H.sub.9 -n OC.sub.2 H.sub.5     blue

EXAMPLE 11

A mixture of 10 g of a 20% strength solution of the compound of theformula (1) in diisopropylnaphthalene and 3.6 g of a 28% strengthsolution of the compound of the formula (18) in diisopropylnaphthaleneor encapsulated with 86.4 g of kerosine in a manner which is known perse with gelatine and gum arabic by coacervation, the capsules are mixedwith starch solution and a sheet of paper is coated with the mixture.

The front side of a second sheet of paper is coated with acid-activatedbentonite as a colour developer. The first sheet and that containing thecolour developer are placed adjacent to one another. Writing by hand orwith a typewriter on the first sheet exerts pressure, and an intenseblack copy which is outstandingly fast to light develops on the sheetcoated with the developer.

EXAMPLE 12

3% solutions with the following composition are prepared from thecolour-forming agents prepared according to the above examples:

a. a colour-forming agent mixture of the formula ##STR63## 60% of whichhas X=OH and 40% of which has X=--OCH₃ in diisopropylnaphthalene,

b. a colour-forming agent mixture of the formula ##STR64## 60% of whichhas X=--OH and 40% of which has X=--OCH₃ in diisopropyldiphenyl,

c. a colour-forming agent mixture of 55% of colour-forming agent mixturea. and 45% of the colour-forming agent mixture b. indiisopropylnaphthalene.

223 parts by weight of solutions a. b. and c. are mixed with 39.5 partsby weight of the diisocyanate of the formula ##STR65##

The mixture is then mixted with 320 parts by weight of an aqueous, 0.5%solution of a partly saponified polyvinyl acetate. The mixture isdispersed to form an emulsion with an average drop size of 7 μm under ashear gradient of a rotor/stator emulsifying apparatus. 76 parts of a9.0% aqueous diethylenetriamine solution are added with stirring to theemulsion formed. In order to allow the microcapsule dispersion to finishreacting it is heated to 60° C. and kept at this temperature for 3hours. A 40% aqueous microcapsule dispersion is obtained.

EXAMPLE 13

250 ml of the 40% microcapsule dispersion obtained with mixture c.according to Example 12 are initially introduced. While stirringvigorously 40 g of finely ground cellulose (®Arbocell BE 600/30manufactured by Rettenmeier und Sohne) are dispersed slowly therein.After stirring vigorously for at least 30 minutes 40 mol of a 50% SBRlatex (®Baystal D 1600 manufactured by BAYER AG) are added. Theresulting 48.5% brushing paint is diluted with water to a 30% solidscontent and is brushed on to the reverse side of a commerciallyavailable base paper. The coat is 5 g/m² when dry. If this paper iswritten on an intensive black copy is obtained on a commerciallyavailable carbon-free paper.

We claim:
 1. A color-forming agent of the formula ##STR66## wherein R¹denotes C₁ -C₁₂ -alkyl or benzyl,X² denotes hydroxyl or C₁ -C₁₂ -alkoxy,R^(3') denotes hydrogen, chlorine, C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy,benzyloxy, phenoxy or a radical of the formula ##STR67## R^(5') denotesa radical of the formula ##STR68## R^(2'), R^(4'), R^(6') and R^(7')independently of one another denote hydrogen, chlorine, C₁ -C₁₂ -alkyl,C₁ -C₁₂ -alkoxy, C₁ -C₄ -alkylamino or di-C₁ -C₁₂ -alkylamino or R^(2')and R^(3') denote members which, together with the benzene ring to whichthey are bonded, complete a ring system of one of the formulae ##STR69##Y denotes C₁ -C₁₂ -alkyl, which unsubstituted or substituted bychlorine, cyano, C₁ -C₄ -alkoxycarbonyl or C₁ -C₄ -alkoxy, or Y denotescyclohexyl, phenyl or benzyl, which are unsubstituted or substituted bychlorine, C₁ -C₁₂ -alkyl or C₁ -C₁₂ -alkoxy, Y¹ and Y² independently ofone another denote C₁ -C₁₂ -alkyl which is unsubstituted or substitutedby chlorine, cyano, C₁ -C₄ -alkoxycarbonyl or C₁ -C₄ -alkoxy, orcyclohexyl, phenyl or benzyl, which can be substituted by chlorine, C₁-C₁₂ -alkyl or C₁ -C₁₂ -alkoxy, or denotes a pyrrolo, pyrrolidino,piperidino, pipecoline, morpholine, pyrazolo or pyrazolino radical whichis unsubstituted or substituted by chlorine, C₁ - to C₄ -alkyl orphenyl.